It looks to me like she's negatively buoyant and is kicking to keep from sinking.
The other thing I noticed (and I'm making an assumption that the guy giving the UP signal to everyone is either an Instructor or DM or at least the person in charge of the group) is a situational awareness thing on this person's part. (And this is simply an observation, not a criticism.)
If you watch the video, he gets a response for the two divers to the left, and gets a response from the buddy of the soon-to-panic diver but not her. In fact, she's looking down and seems to be flailing already. He gives the signal again but no response from her. IMHO, this is when he should have made a move towards her because something;'s not right. (And I'm ignoring the entire why-isn't-her-buddy-aware-of-this-too train f thought.)
He then signals another diver approaching the left group and gets a response. He appears to then begin the ascent and glances right (and you can see her struggling already), check his gauge, and then looks to the right again.
At this point, you can see she's struggling, he's above her, she's already above her buddy and that means neither one of them can provide immediate assistance. You can then hear an audible GULP as she rips her mask off and starts to bolt. I'm amazed her was able to get her to take the reg back, and she did so without her mask on her face.
The other thing I notice is that, once the reg is back in her mouth (presumably - it's hard to tell with the bubbles), he appears to not take hold of her or do anything to try to control her or the ascent (although he does appear to be holding her right wrist at the surface). I'd rather have seen him grab her armpit (I'm a big fan of human contact helps control panic) or at least her BC or even her tank valve. Because she could just as easily have spit the reg back out and gone up or down.
The other thing that bugs me a bit is that, once she's on the surface, no one's inflating her BC, or ditching or just taking her weights, or even saying anything to her. All you hear is her gasping. Granted, the video cuts off after that but I think there should have been some reassuring/assessing going on.
Here's the scary takeaways from a timing standpoint:
0:17 - First UP sig to her
0:19 - Second UP sig to her
0:30 - She's struggling
0:40 - He realizes something's wrong (he sculls his hand up to push himself down)
0:41 - She rips off mask and spits out her reg
0:46 - He attempts to hand her octo
0:51 - His octo goes in her mouth
0:54 - They're ascending (unknown depth)
1:09 - They surface (15 seconds after they started)
1:24 - Video ends
So from the point of the second non-response to the panic, it's 22 seconds. So I think one of the takeaways here, especially for anyone newly-certified or new DMs or Instructors, is that while this stuff happens quickly, IF you're situationally aware, there's enough time to POSSIBLY (speculation) prevent the incident from happening.
And it's also important to remember, and this is where the situational awareness comes in, that panic doesn't just suddenly appear out of nowhere. It's a step-by-step process that builds (slowly or quickly) and results in panic. But you may have time (in this case, at least 22 seconds) to react.
And the other takeaway is you're a dive leader is to remember that your job is not simply to get people from Point A to B and back to A. Rightly or wrongly, they may be relying on you more than you realize. personally, I'd rather over-react than under-react. Also makes it much easier to sleep at night feeling you did everything reasonably possible, rather than second-guessing and thinking "If only I had . . ."
- Ken